Means for determining drilling fluid characteristics



Oct. 4, 1938. w H COLLINS 2,132,015

MEANS FOR DETERMINING DRILLING FLUID CHARACTERISTICS Filed Feb. 19, 1937 Patented Oct. 4, 193$- UNITED STATES PATENT orricr.

Application February 19, 1937, Serial No. 126,592

.lclaim.

In the drilling of oil wells by the rotary method it is the practice to circulate a drilling fluid downwardly through the drill stem as it rotates. outwardly through the drill bit, and upwardly through the well bore outside of the drill stem to the surface. This circulation of drilling fluid serves many purposes, such as the carrying away a of the cuttings from the drill bit, the cooling of the drill bit, the maintaining of a pressure against the wall of the formation so as to prevent caving and to prevent the inrush of foreign substances from the formation, as well as to overcome gas pressures which are encountered by the drill bit.

It is obvious, therefore, that the characteristics of the drilling fluid must be accurately known and controlled at all times in order that all of its varied functions may be properly performed. .The weight must be accurately controlled in order that the desired pressure will be exerted on the formation to prevent blowing outof the well. The viscosity ofthe fluid must be .accurately controlled so as to obtain proper circulation without excessive friction losses and to insure that the mud will not become fllled with gas or gas cut, that is carrying an excessive amount of gas in suspension. The gelling qualities of the mud must also be known because in some instances the drilling operation is shut down and if there is too great a tendency of the mud to gel, then.

of course, it would stick the drill pipe and prevent further operation in the well and, lastly, it is desirable to know the sand content of the mud so that the size of the slush pit can be varied or the'volume oi mud used for the drilling operation controlled, so as to permit the sand to settle out of the mud or to removeit by proper chemical or mechanical means.

It is one of the objects of the invention to provide an apparatus which can be readily utilized to ascertain all four of the foregoing characteristics in a minimum of time on the derrick floor.

Another object of the invention is to provide a hydrometer and viscosimeter for use with on drilling fluid. Still another object of the invention is to provide a container having graduations thereon to indicate the amount of immersion of the' container in a liquid and a window therein to ascertain the level of the contents in the container.

Other and further objects of the invention will be readily apparent when the following description is considered in connection with the accompanying drawing wherein:

Fig. 1 is a vertical sectional view showing the 5 arrangement and relative position of the parts when the weight per gallon of a sample of the drilling fluid is being determined.

Fig. 2 is a vertical sectional view showing one manner of obtaining the gelling qualities of a 10 sample of the drilling fluid.

Flg. 3 shows a modified form of container whereby. the level of the fluid therein can be accurately determined.

Fig. 4 is a section taken on the line 4-4 of 15 Fig. 3.

In Fig. l a receptacle 2 has been generally illustrated which contains a body of water 3. This body bf water is of suflicient depth to float the container 4 when it contains a predetermined body of drilling fluid 5. As seen in the drawing, the drilling fluid has a greater specific gravity than that of water because the volume of water displaced is greater than the volume of the drilling fluid, and-the amount of immersion of the container or tube 4 can be readily ascertained by observing the graduations l on the side thereof as an indication of the specific gravity or weight per gallon of the sample of drilling fluid.

A predetermined volume of drilling fluid 5 has been placed in the container 4 and this volume is indicated by the graduations 9 on a window 16 in the side of the tube. In this manner the volume can be accurately determined and, as seen in Fig. 1, there are other graduation lines on the window, such as H and I2. As an illus tration, the line l2 may indicate 500 cubic centimeters. Theline Ii may indicate 1000, and the line 9 indicate 1500. Any other units of measurement may, of course, be used.

The graduations 1 may be calibrated in any desired manner but the practice in the drilling industry is to indicate the specific gravity of the drilling fluid by the pounds per gallon and it is the usual practice to use drilling muds which vary from 9 to 12 pounds per gallon. In some instances muds having greater or lesser weights are also used. Of course, the weight of water is well known to be 8.3 pounds per gallon.

The container 4 is provided at its base with an orifice l5 which may be in the form of a stop cock i5. This stop cock may beopen or closed as-desired in order to permit a flow of fluid from the container. This container may be made of provided and by suitable computation the viscosity can be determined.

This container of Fig. 1 is of particular advantage because if the weight per gallon and the viscosity are to be determined it is only necessary to dispose a predetermined volume of drilling fluid in the container, immerse it in the water in the receptacle 2, so as tov read the weight per gallon directly from the graduation l. The container is then removed and the stop cock it opened so that the time may be observed which is required for this body of drilling fluid to escape from the container. Thus in a very short period of time and with very little difficulty the weight and viscosity of the fluid can be determined very accurately so that readings can be taken very frequently as the drilling fluid discharges or enters the well.

In Fig. 2 one manner of ascertaining the gelling tendency of the drilling fluid is shown. In this arrangement the receptacle 2 contains a.v body 20 of drilling fluid which is, of course, similar to the drilling fluid at 5. In this form the container d has a body of water 2| disposed therein of a predetermined volume, as indicated by the level line 22 on the window 23.

' A number of graduations 24 are shown on the periphery of the tube or container d which may be used to indicate the extent of the immersion of the tube in the drilling fluid 20. Inasmuch as the weight per gallon of the drilling fluid 20 is known,'then of course a predetermined volume of water, as at it, should displace a predetermined volume of the drilling fluid. If, however,

I the drilling fluid has a tendency to gel there will be an increase in the frictional resistance around the outside of the tube due to this tendency, and the tube will not sink into the drilling fluid the proper amount. This tendency to gel is determined over difi'erent periods of time. -A sample of the drilling fluid may be taken from the return line and placed in the receptacle 2 and the container 4 immediately placed therein. The amount of initial gel is thus determined. The container is then removed and after a period of five minutes the tube may be again inserted and again observed, and this will be known as the five-minute gel. These indications may be carried on for ten or fifteen minutes or other periods of time as desired so that the tendency to gel and to cause difficulty in the well bore can be readily observed.

In order to obtain an accurate test of the viscosity various volumes of the drilling fluid may be placed in the container 41. For instance, the first test may consist of depositing 1500 co. in the container and observing the time necessary to withdraw 1000 cc. thereof. The next test may consist of depositing 1500 cc. in the container and withdrawing 500, while the third test may consist of putting in 500 and withdrawing 500. Thus, an average of the times for the volumeconsidered may be taken and in this manner a balance obtained for-the various friction losses.

In order to determine the sand content of a sample of the drilling fluid a predetermined volume may be placed in the container 6 and any desired amount of water added thereto. Agitation'of the water and the drilling fluid results in its. dilution so that the heavier particles of sand will have a tendency to settle to the bottom. The liquid can be removed from the top and the operation repeated until only clear water remains in the tube with the sand settled at the base thereof, for the purpose of ascertaining the percentage of sand as compared with the original volume of drilling fluid which was placed in the container. As an example, if 1,000 cc. of drilling fluid to the level of line H was originally placed in the tube and the graduations 25 show the level of the sand which remains, it is an obvious calculation to determine the percentage of sand which was present in the sample of drilling fluid.

A list of the colloidal properties of the drilling mud may be made'with the container d by depositing /a given quantity of water therein and thoroughly mixing with it a small percentage of mud. When allowed to stand the amount of the mud which settles out of the water is an indication of the colloidal properties. The graduations may be used to.indicate the percentages.

Another form of ascertaining the gel qualities of the mud would be to dispose samples of the mud sample with respect to the mud in the container.

A modified form of the container 8 is illustrated in Fig. 3 where the container is composed of a lower portion 30 and an upper portion 3|. These two parts are interconnected by the joint 32 and the upper portion 3i having an opening 33 therein and the lower portion 30 having an opening 35. Normally these openings are out of alignment, as seen inFig. 4, but by relative rotation of the parts they may be moved into alignment. Thus any liquid in the container would flow out the opening 35 down to the level of the bottom of the openings as at 35 in Fig. 3. In this manner if the container were solid metal or other opaque material the level could be accuratelydetermi ned without the provision of the windows, such as H] or 23 shown in Figs. 1 and 2, respec-* tively. It is to be understood that the container of Figs. 1 and 2 may be the same container with the graduations and windows on opposite sides thereof if desired.

Broadly the invention contemplates a simple and economical means for determining the four characteristics of a drilling fluid which are essential to its proper use. 

